PSE15 after re-install

I had to re-install PSE15 after my Windows 10 died , Ive imported all the pictures saved on an external hard drive , initially when i click on the folder it open and thumbnails are visible for a nano second then they turn grey with an "egg-timer" in the middle if i double click a thumbnail it opens up the file but its grey and again with the egg-timer , if i then double click it again it then opens up the picture correctlyIve got nearly 10K picture and really really don't want to have to do this every time